Method and apparatus for forming a beam of charged particles

ABSTRACT

Charged particles are concentrated and held in space by means of an unequal, alternating electric field and the resulting beam of particles is directed through a hole in a plate electrode to a target electrode. A gate electrode adjacent the plate electrode may be operated selectively to oppose and enable the passage of the concentrated beam of charged particles to the target.

llnited States Patent 1191 Masuda 1451 Apr. 3, 1973 [54] METHOD AND APPARATUS FOR [56] References Cited FORMING A BEAM 0F CHARGED TED STATES PATENTS PARTICLES 3,316,443 4/1967 Hansen ..313/63 X [76] Inventor: Senichi Masuda, l-40-10-605 3,519,942 7/l970 Mobley ..313/63 X Nishigahara Kim Japan 3,402,358 9/1968 Wharton ..328/233 7 3,122,882 3/1964 Schultz et al. ..3l3/63 x [22] Filed: Apr. 23, 1971 3,178,601 4/1965 Cleland ..3l3/63 3,366,886 1/1968 Dryden r ..328/233 21 Appl. No.: 136,967

[30] Foreign Application Priority Data Apr. 28, 1970 Japan ..45/36500 [52] US. Cl. ..328/228, 313/63, 315/168, 328/233 [51] Int. Cl. ..H01j 29/58 [58] Field of Search .313/63; 315/111, 168; 328/228, 328/233 Primary Examiner-Palmer C. Demeo Attorney-Oliver D. Olson [5 7] ABSTRACT Charged particles are concentrated and held in space by means of an unequal, alternating electric field and the resulting beam of particles is directed through a 11 Claims, 9 Drawing Figures PATENTEUAFR3 I975 SHEET 1 [IF 5 SENICHI MASUDA INVENTOR.

BY CQQQ'AQQW AGENT PATENTEDAPR3 I973 SHEET 2 [1F 5 G AW O.

J Q W G "Si- I NICHI MASUDA IN NTOR.

AGENT PAn-ir-minma ma 3,725,797

SHEET 3 BF 5 SENICHI MASUDA AGENT PATENTEDAPR3 I975 SHEET u 0F 5 AGENT PATEN-TEDAPM 1975 sum 5 OF 5 SE NJICHI MASUDA INVENTOR BY @m AGENT METHOD AND APPARATUS FOR FORMING A BEAM F CHARGED PARTICLES The present invention relates to method and apparatus for forming a charged particle cloud confined in an electric field and provides method and apparatus effectively utilizable in the field of powder technology, in electrostatic painting, development in electrophotography, electrostatic selection and printing, drawing and processing by means of a charged beam, etc.

The electric field curtain apparatus is able to confine a cloud of charged particles within a space without any contact with the components by means of an unequal alternating field, and to block the migration of the charged particles to other regions.

The principal object of the present invention is to form a concentrated cloud of charged particles confined within an electric field.

Another object of the present invention is to provide for the direction of such a cloud to a target in the form of a concentrated beam.

A further object of the present invention is to provide for the selective passage of such a concentrated beam to a target by applying a voltage to a gate electrode.

The apparatus of the present invention involves the provision of a plate electrode at an appropriate distance from one end of a plurality of spaced annular electrodes arranged to produce an unequal alternating electric field curtain apparatus at the end of said electric charged particles introduced at the opposite end of the electrode assembly and are are retained in space by the unequal alternating electric field. A hole in said plate electrode provides for the passage of the charged particles in the form of a beam to a target electrode located next to said plate electrode.

The method and apparatus of the present invention will be fully understood by the following explanation taken in connection with the accompanying drawings, in which:

FIG. 1 is a schematic view, partially in perspective, of apparatus embodying the features and illustrating the method of the present invention,

FIG. 2 is a fragmentary view, taken along the line lI-II in FIG. 1, showing the alternating electric field associated with the annular electrodes of FIG. 1;

FIG. 3 is a fragmentary view taken along the same line as FIG. 2 and showing the arrangement of charged particles produced by the alternating electric field of FIG. 2;

FIG. 4 is a fragmentary view, similar to FIG. 2, showing the alternating electric field associated with the plate electrode of FIG. 1;

FIG. 5 is a fragmentary view, similar to FIG. 3, showing the arrangement of charged particles produced by the alternating electric field of FIG. 4.

FIG. 6 is a fragmentary view, similar to FIG. 3, showing the arrangement of charged particles produced by the combination of alternating electric field and direct current electric field.

FIG. 7 is a fragmentary view, similar to FIG. 6, showing the association of the charged particles with the plate electrode.

FIG. 8 is a fragmentary view, similar to FIG. 7, showing the association of the charged particles with the plate and target electrodes.

FIG. 9 is a fragmentary view, similar to FIG. 8, showing the association of a gate electrode with the plate and target electrodes.

Basically, this invention involves the provision of an electric field which includes one component capable of concentrating charged particles along a longitudinal axis and another component capable of moving the concentrated particles along said longitudinal axis toward a target. In one embodiment of this invention, said one component is provided by a single phase alternating current and the other component is provided by a direct current. In a second embodiment, both components are provided by a multi-phase alternating current.

Referring now to FIG. 1, 1 are annular electrodes, 2 alternating high tension apparatus, 3 direct current power source which is supplied by division to each of the annular electrodes as shown in the figure. 8 are condensers, provided by necessity for applying alternating and direct currents in superposition to the annular electrodes 1. The assembly of components 1, 2,3 and 8 is called an electric field curtain apparatus. 4 and 5 are direct current sources 6 a plate electrode and 7 a target electrode.

The assembly of electrodes may be supported by any suitable means and the apparatus operated under normal atmospheric conditions, since it is not required that the apparatus be housed in an evacuated chamber. This renders the apparatus suitable for many uses, since the target electrode may be of any desired form in any desired environment.

FIGS. 2 and 3 show how a charged particle cloud is confined within small a space by the application of alternating current. As shown in FIG. 1 the annular electrodes l are connected alternately with an alternating current source, and thus opposing alternating electric fields are established in the adjacent intervals of electrodes. Now if we consider an instant, the polarities of the electrodes will be as shown in FIG. 2 and the resulting electric lines of force will be as shown by 9. The charged particles, provided by any conventional means and introduced within this electric field, move along the electric lines of force 9, but undergo oscillatory motion due to the alternating electric fields. Since the electric lines of force 9 are curvilinear and centrifugal force will be effective, the charged particles are pushed to the center of the circle of each electrode and therefore are held in space at the central part of the annular electrode while maintaining oscillatory motion under the influence of the alternating electric field. FIG. 3 shows how the charged particles 10 are held at the central parts of annular electrodes 1.

Next, as shown in FIG. 4, although a plate electrode 6 is positioned forwardly of the end electrode 1 a distance equal to one-half the distance between adjacent annular electrodes, only one half the alternating current voltage is supplied to it, whereby, the aspect of the electric field is not changed. In FIG. 4 the arrows showing the direction of electric lines of force 9 are eliminated. Here, though the annular electrode l-b on one side of the plate electrode 6 is taken off, the appearance of the electric field, as shown in full lines in FIG. 4, will not be changed. It appears as if annular electrode l-b is existing and the electric lines of force 9-a and 9-11 are in continuity. Ifthe charged particles 10 are introduced in such a state as the above, the ap pearance shown in FIG. 5 will be obtained and the ends of the group of annular electrodes will present the same appearance with the other.

Next, if direct current is supplied by subdivision to the group of annular electrodes, as shown in FIG. 6, the charged particles will move along the electric field due to the direct current. That the appearance becomes as shown in FIG. 6 will become clear from the distribution of the electric lines of force shown in FIG. 2. That is, the charged particles are constricted between the annular electrodes. The degree of constriction is most intense just at the central portion between the annular electrodes.

When the plate electrode 6 is supplied, as by source 4, with half the direct current voltage as is supplied by sources 3 to the annular electrodes, and at the same time half the alternating current voltage is placed at just the central position between the annular electrodes and a further annular electrode at the other side of the plate electrode is removed, it will be clear from the above explanation that there will be obtained the appearance shown in FIG. 7. That is, the charged particle cloud 10 will come in contact, intensely constricted, with the surface of the plate electrode 6.

Next will be explained the method of forming the thus focused charged particle cloud into a beam. For that purpose, as shown in FIG. 8, a hole 6-b is provided for letting the charged particles 10 pass through the plate electrode 6 at the position where said charged particles would touch. A target electrode 7 is provided in front of the plate electrode. If we apply a direct current voltage between the plate and target electrodes, the charged particles 10 will be directed to the target electrode 7. 11 is the electric lines of force established by the plate electrode 6 and the target electrode 7 and by the provision of this electrode the focused, charged particles are caused to arrive at a target object as a beam, without scattering.

Another example of an apparatus for forming the charged particle cloud into a beam is shown in FIG. 9. Passage of the charged particles to the target electrode can be controlled by providing a gate electrode 12 near the plate electrode 6. Thus, at times a voltage for prohibiting the beam from passing from the plate electrode 6 to the target electrode is applied to the gate electrode 12, while at other times a voltage for passing the beam is applied in pulse form, as shown. Then the charged particles fly to the target electrode 7 as a small lump. The quantity of the particles can be controlled by the voltage and interval of the pulses. The gate electrode 12 is bored to provide a hole which can pass the charged particles.

It is to be understood that the present invention is not limited to the apparatus illustrated and described hereinbefore and modifications which do not change the essential features of the present invention belongs within the scope of the present invention.

For example, the electrode assembly constituting the electric field curtain apparatus may have such a construction as to be able to hold the charged particle cloud in space without coming in contact with others, as with quadrupole electrodes. And although, in the above explanation, an example is given in which single phase alternating current and direct current are superposed, yet, if we use multiphase alternating current, a shifting electric field will be produced in the direction of phase rotation, so that the direct current source 3, 4 and condensers 8 are necessary. In the above explanation the position of the plate electrode 6 and the applied voltage are said to be middle and half value, respectively. However, in the case where we do not mind any small disturbance of the distribution of the electric field, or do not require a most finely constricted beam, then the above position or voltage may be adequately increased or decreased.

I claim:

1. The method of forming a beam of charged particles, comprising:

a. producing an elongated electric field having one component capable of concentrating charged particles along a longitudinal axis and another component capable of moving the concentrated particles along said axis to a target,

b. introducing charged particles into the elongated electric field at one end thereof, whereby to effect concentration of the particles within said field and movement of the particles axially toward the opposite end of said field, and

. producing between said opposite end of the electric field and a forwardly positioned target a direct current electric field, whereby to direct the concentrated beam of particles to the target without scattering.

2. The method of claim 1 including producing adjacent the direct current electric field an intermittent gating electric field for selectively opposing and enabling the passage of the concentrated beam to the target.

3. The method of claim 1 wherein said one component of the electric field is formed by a plurality of alternating electric fields of alternately unequal polarity produced by single phase alternating current, and the other component of the electric field is produced by direct current.

4. The method of claim 3 wherein the electric field is arranged to effect substantially maximum concentration of the charged particles in areas disposed to opposite sides of each of the plurality of alternating electric fields at distances substantially equal to one-half the distance between said alternating electric fields, and the target-directing direct current electric field is produced between the forwardmost area of maximum concentration of particles and the target.

5. The method of claim 1 wherein both components of the electric field are produced by a multi-phase alternating current.

6. Apparatus for forming a beam of charged particles, comprising a. means for producing an elongated electric field having one component capable of concentrating charged particles along a longitudinal axis and another component capable of moving the charged particles along said axis to a target,

b. whereby the introduction of charged particles into the elongated electric field at one end thereof effects concentration of the particles within said field and movement of the particles axially toward the opposite end of said field,

c. target means forwardly of said opposite end of the electric field producing means, and

d. means for producing between said opposite end of the electric field and said target means a direct current electric field, whereby to direct the con- W centrated beam of particles to the target without scattering.

7. The apparatus of claim 6 including means for producing adjacent the direct current electric field an intennittent gating electric field for selectively opposing and enabling the passage of the concentrated beam to the target.

8. The apparatus of claim 6 wherein a. the means for producing the electric field comprises l. a plurality of axially aligned and spaced-apart annular electrodes, and

2. a source of alternating current potential connected to the electrodes alternately in unequal polarity or phase, and

b. the means for producing the target-directing direct current electric field comprises 1. a plate electrode positioned forwardly of the forwardmost annular electrode, the plate electrode having an opening therethrough in axial alignment with the annular electrodes,

2. a source of alternating current potential connected to the plate electrode, and

3. a source of direct current potential connected across the plate electrode and target means.

9. The apparatus of claim 8 wherein a. the source of alternating current potential is single phase and is connected to the annular electrodes alternately in opposite polarities, and b. the apparatus includes 1. capacitance means connecting the source of alternating current potential to each electrode, and 2. a source of direct current potential connected to each electrode. 10. The apparatus of claim 9 wherein a. the plate electrode is positioned forwardly of the forwardmost annular electrode a distance equal substantially to one-half the distance between annular electrodes,

- b. the source of alternating current potential for the plate electrode is substantially one-half the magnitude of the alternating current potential for the annular electrodes,

c. the source of direct current potential for the plate electrode is substantially one-half the magnitude of the direct current potential for the annular electrodes, and

d. the target means is positioned forwardly of the plate electrode a distance equal substantially to one-half the distance between annular electrodes.

1 1. The apparatus of claim 8 including a. a gate electrode adjacent the plate electrode having an axially aligned opening therethrough, and

b. a source of gating potential connected to the gate electrode for selectively opposing and enabling the passage of the concentrated beam of charged particles to the target. 

1. The method of forming a beam of charged particles, comprising: a. producing an elongated electric field having one component capable of concentrating charged particles along a longitudinal axis and another component capable of moving the concentrated particles along said axis to a target, b. introducing charged particles into the elongated electric field at one end thereof, whereby to effect concentration of the particles within said field and movement of the particles axially toward the Opposite end of said field, and c. producing between said opposite end of the electric field and a forwardly positioned target a direct current electric field, whereby to direct the concentrated beam of particles to the target without scattering.
 2. The method of claim 1 including producing adjacent the direct current electric field an intermittent gating electric field for selectively opposing and enabling the passage of the concentrated beam to the target.
 2. a source of direct current potential connected to each electrode.
 2. a source of alternating current potential connected to the plate electrode, and
 2. a source of alternating current potential connected to the electrodes alternately in unequal polarity or phase, and b. the means for producing the target-directing direct current electric field comprises
 3. a source of direct current potential connected across the plate electrode and target means.
 3. The method of claim 1 wherein said one component of the electric field is formed by a plurality of alternating electric fields of alternately unequal polarity produced by single phase alternating current, and the other component of the electric field is produced by direct current.
 4. The method of claim 3 wherein the electric field is arranged to effect substantially maximum concentration of the charged particles in areas disposed to opposite sides of each of the plurality of alternating electric fields at distances substantially equal to one-half the distance between said alternating electric fields, and the target-directing direct current electric field is produced between the forwardmost area of maximum concentration of particles and the target.
 5. The method of claim 1 wherein both components of the electric field are produced by a multi-phase alternating current.
 6. Apparatus for forming a beam of charged particles, comprising a. means for producing an elongated electric field having one component capable of concentrating charged particles along a longitudinal axis and another component capable of moving the charged particles along said axis to a target, b. whereby the introduction of charged particles into the elongated electric field at one end thereof effects concentration of the particles within said field and movement of the particles axially toward the opposite end of said field, c. target means forwardly of said opposite end of the electric field producing means, and d. means for producing between said opposite end of the electric field and said target means a direct current electric field, whereby to direct the concentrated beam of particles to the target without scattering.
 7. The apparatus of claim 6 including means for producing adjacent the direct current electric field an intermittent gating electric field for selectively opposing and enabling the passage of the concentrated beam to the target.
 8. The apparatus of claim 6 wherein a. the means for producing the electric field comprises
 9. The apparatus of claim 8 wherein a. the source of alternating current potential is single phase and is connected to the annular electrodes alternately in opposite polarities, and b. the apparatus includes
 10. The apparatus of claim 9 wherein a. the plate electrode is positioned forwardly of the forwardmost annular electrode a distance equal substantially to one-half the distance between annular electrodes, b. the source of alternating current potential for the plate electrode is substantially one-half the magnitude of the alternating current potential for the annular electrodes, c. the source of direct current potential for the plate electrode is substantially one-half the magnitude of the direct current potential for the annular electrodes, and d. the target means is positioned forwardly of the plate electrode a distance equal substantially to one-half the distance between annular electrodes.
 11. The apparatus of claim 8 including a. a gate electrode adjacent the plate electrode having an axially aligned opening therethrough, and b. a source of gating potential connected to the gate electrode for selectively opposing and enabling the passage of the concentrated beam of charged particles to the target. 